Acid phosphatase activity and vesicular‐arbuscular mycorrhizal infection associated with roots of four wheat cultivars

Acid phosphatase activity and vesicular‐arbuscular mycorrhizal (VAM) infection associated with four spring wheat genotype roots were investigated. Plants were grown in a typic low P volcanic soil with and without P‐fertilizer addition and harvested at 21, 42, 63, 84 and 96 days. Results show that phosphatase activity, expresed as ug p‐nitrophenol released per g dry root, decreased from 21 to 96 days in all cultivars. Conversely, trends of VAM infection were similar in all genotypes being higher in P added plants at 63 days after sown. This opposite effects may be viewed as alternative and/or complementary adaptations for P‐uptake by plants growing in low nutrient situations. It was concluded that one of the ways of P‐alleviation in wheat growing in our volcanic soils might be the search of genotypes having high biochemical and/or biological root activities.     

Effects of water‐soluble constituents of plant residues on water uptake by seeds

Abstract

There has been strong support for the hypothesis that the adverse effects of plant residues on crop yields are due to phytotoxic compounds derived from these residues. This hypothesis is based largely on studies showing that, when compared with distilled water, aqueous extracts of plant residues have an adverse effect on seed germination and seedling growth. Because seed germination and seedling growth are reduced by a delay in germination resulting from slow uptake of water by seeds, we studied the possibility that the adverse effects of aqueous extracts of plant residues on seed germination and seedling growth might be at least partly due to water uptake by seeds being retarded by water‐soluble constituents of these residues. To test this possibility, we compared the rates of water uptake and germination of seeds of corn (Zea mays L.), soybean [Glycine max. (L.) Merrill], and wheat (Triticum aestivum L.) when these seeds were treated with distilled water and with aqueous extracts of corn, sorghum [Sorghum bicolor (L.) Moench], and wheat residues. We found that the rates of water uptake and germination of seeds treated with aqueous extracts of plant residues were appreciably slower than the corresponding rates for seeds treated with distilled water. This may be due to the water potentials of these extracts (ca. ‐50 kPa) because when seeds of corn, sorghum, and wheat were treated with a solution of polyethylene glycol 8000 having a water potential similar to that of the extracts of plant residues tested, the rates of water uptake and germination were also slower than the corresponding rates for seeds treated with distilled water. These observations suggest that the adverse effects of aqueous extracts of plant residues on seed germination and seedling growth when compared with distilled water may be partly due to constituents of these extracts inducing water potential effects that reduce water uptake by germinating seeds.     

Long‐term root uptake of radiocesium by several crops

Abstract

A greenhouse study was conducted to evaluate the long‐term availability of radiocesium (Cs‐137) to various crops grown on contaminated soil that were limed to pH 6.8 (LIME) or were limed and Zn‐ and Mn‐EDTA chelates added (LIME + CHELATE). Crops were grown either continuously or followed a cropping sequence. Continuously grown clover and bahiagrass accumulated the most Cs‐137 with levels exceeding 2,000 pCi/g dry weight in bahiagrass. Uptake of Cs‐137 was depressed by both the LIME and LIME + CHELATE treatments. Uptake was usually greatest during the first three years but only in unlimed soil. Cesium‐137 is about 3 to 8 times higher in soybean beans than in wheat grain. Uptake of Cs‐137 by plants from contaminated soil can be expected to be high in acidic soils, especially in the absence of lime treatment.     

Comparing cultivars of three cool‐season turf‐grasses for potassium uptake kinetics and potassium recovery in the field

Efficient use of potassium (K) by turf depends on the ability of roots to absorb a high proportion of the fertilizer K applied to the soil. Among turfgrass genotypes, variation in K absorption kinetics of roots and its inheritance is important in the development of genotypes that are more efficient in K absorption from the soil. Therefore, K uptake kinetics of six cultivars each of Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) were compared under greenhouse conditions. In 1990 and 1991, field studies of the same cultivars were conducted comparing clipping production rate, leaf blade K concentration, K recovery rate in clippings, K efficiency ratio and visual quality under a moderate K fertilization of 59 kg K/ha/year. Significant differences among species and cultivars were obtained for both absorption kinetics and field recovery of K. Significant correlations between some K uptake parameters and field performance were identified. These results show that genetic differences exist among turfgrasses for K utilization at both the interspecific and intraspecific levels and suggest that a screening program could be developed to identify turfgrass genotypes possessing superior K utilization.     

Sulfate uptake by salinity‐tolerant plant species

Abstract

High soluble‐sulfate (SO₄) concentrations affect water quality, soil chemistry, plant sulfur (S) levels, and possibly ruminant‐animal health. The objective of this greenhouse pot study was to determine the potential for accumulating high levels of S by tansy mustard (Descurainia pinnata (Walt.) Britton), kochia (Kochia scoparia L. Schrad.), yellow sweet clover (Melilotus officinalis L.), slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners), and sunflower (Helianthus annuus L.). Plants were grown on both a Brinegar (fine‐loamy Ultic Argixeroll) and Portneuf (coarse silty Durixerollic Calciorthid) soil. Each species received five‐SO₄ levels. The saturation extract electrical conductivity (EC) of the cropped soils ranged from 6 to 16 dS/m, while the soluble SO₄ varied from 16 to 200 mmol_c/kg soil. Soil solutions were saturated or very nearly saturated with respect to gypsum at the conclusion of each study. Plant dry matter yield, except of grass growing on the non‐calcareous soil, was not reduced by SO₄ treatment nor by the sulfate‐induced decrease in mole fraction of calcium (Ca)/(sum cations) to values less than 0.10 for kochia and grass. Sulfur concentration in the plants ranged from 2.5 mg/g in grass to 10 mg/g in mustard and for each species was linearly related to the SO₄ treatment and soil‐SO₄ activity. Plant SO₄‐S values ranged from 70 μg/g in the grass to nearly 900 μg/g in mustard. Total nitrogen (N): organic S was 4.4, 7.5, 11.4, 16.5, and 5.8 for mustard, kochia, clover, grass, and sunflower, respectively. It was concluded that these species could accumulate high levels of S in the above ground tissue.     

Nitrogen‐uptake by plants following soil incubation

Abstract

Many methods of evaluating organic soil nitrogen (N) mineralization and N availability indexes have been proposed. Chemical methods are more rapid but they do not measure the soil microorganisms and plant root activities. Incubation‐leaching procedure may remove some of the readily mineralizable soil organic N compounds. Continuous‐incubation procedure may sometimes increase soil acidity or cause toxins accumulation. The objective of this study was to determine, in a greenhouse experiment, the relative capabilities of 10 soils with organic matter (O.M.) content ranging from 2.38 to 8.63% to supply plant‐available N by combining two procedures, i.e., soil incubation and plant N‐uptake. In method one (M₁), N‐uptake by 3 successive oat crops of 8 weeks each, without soil preincubation was studied. Method two (M₂) involved a soil preincubation of 8 weeks, and the subsequent determination of N‐uptake by two successive crops of oats (Avena sativa L.) of 8 weeks each. No soil‐leaching was used. The results show that there was a large difference in plant N‐uptake according to soil organic matter. The highest correlation between soil O.M. and plant N‐uptake (r = 0.91**) was given by the first crop following incubation. The N‐uptake by the first crop in M₁ (without soil incubation) was much less correlated with soil O.M. (r = 0.74*) and was significantly influenced by soil initial NO₃ and NH₄‐N. The results of this study show that the preincubation of soil samples minimized the influence of soil initial mineral N and that a preincubation was necessary before the plant N‐uptake measurement, even on a 8‐week cropped soil period.     

Effects of sulfur nutrition on photosynthesis in cadmium‐treated barley seedlings

The effects of sulfur (S) nutrition at 0.1 or 1 mM S on cadmium (Cd) toxicity measured by photosynthesis in barley (Hordeum vulgare L. cv. UC 476) seedlings were studied. Eight‐day‐old seedlings were treated with 25 μM Cd by adding cadmium chloride (CdCl₂) to the nutrient solution. Then photosynthetic carboxylation efficiency (ACi curve) and stomatal conductance of the primary and second leaves were measured at four and eight days after Cd treatment. Fluorescence parameters were measured every 24 h for eight days after two days of Cd treatment. At 20 days, plant growth parameters were measured and dry biomass determined. The results showed that ACi was significantly reduced by Cd, but more in the low (0.1 mM) S than in the high (1 mM) S‐treated plants. Stomatal conductance of plants was also decreased by Cd, but more in the low S‐treated plants. Low S‐treated plants exposed to Cd showed an increase in Fo and Fq, and a decrease in Fv/Fm and T_1/2, indicating photoinhibitory damage to PSII. Analysis of the growth parameters showed that Cd decreased plant size and biomass, but the reduction was more severe in the low S‐treated plants. These results support the hypothesis that S is a critical nutritional factor in plants which is important for the reduction of Cd toxicity.     

Effects of photoperiod and photosynthet1c photon flux on nitrate content and nitrate reductase activity in greenhouse‐grown lettuce

Lettuce plants (Lactuca saliva, cvs ‘Karlo’ and ‘Rosana') were subjected to three light levels (0, 50, and 100 μmol/m²/s) provided by supplementary lighting. Photoperiods extended to 16 h, 20 h, 24 h, and 24/16 h were compared with natural light in the course of five greenhouse trials. The use of supplementary lighting significantly reduced nitrate concentration in the leaves during the winter. Total nitrate reductase enzyme activity in terms of whole plants was higher owing to an increase in light levels, whereas there was no significant difference in terms of fresh weight for the various light treatments. Fluctuations in nitrate reductase activity were observed over a 24‐hour cycle. Enzyme activity was the lowest between 11:00 a.m. and 1:00 p.m. Nitrate concentration and nitrate reductase activity were the highest in the outer leaves.     

The effect of subsurface aluminium on the growth and uptake of surface‐applied phosphorus by wheat seedlings 1

Seedlings of four cultivars of wheat (Triticum aestivum L.) differing in tolerance to aluminium (Al) were grown for 14 to 20 days using a split‐root sand/solution culture technique. Each culture tube was divided horizontally into two compartments by a root‐permeable paraffin wax barrier, so that phosphorus (P) and aluminium (Al) supply could be varied in the upper 0–80 mm (surface) and lower 80–180 mm (subsurface) compartments, respectively.

Root growth into the subsurface zone was enhanced by increased P supply to surface roots, but only in the absence of subsurface Al. Where subsurface Al was present, increased P supply to surface roots had no effect on the penetration of roots into the subsurface zone. Tolerance to Al in the cultivars used was therefore not related to the ability to translocate P to sites of Al injury.     

Phosphorus sorption by four soils receiving long‐term applications of fertilizer

Abstract

A laboratory study was conducted to evaluate P sorption in the Ap horizon of four soil series in the Ultisol order (Benndale Is, Hartsells fsl, Lucedale fsl, and Dewey sicl) receiving the same fertility treatments since 1929. Soil was collected in the spring of 1985 from 4 treatments: i) no‐lime, plus P (total fertilizer P = 1584 kg/ha from 1929 to 1985); ii) no‐K, plus P (total fertilizer P = 1584 kg/ha); iii) low‐P (total fertilizer P = 442 kg/ha); 4) standard treatment (total fertilizer P = 2376 kg/ha). The soils and treatments within a soil varied in pH, total P, Mehlich 1 extractable P, K, Ca and Mg, and KC1 extractable Al. The four soils had large differences in P sorption capacity which increased with increasing clay content. The Dewey (27 % clay) soil had the highest P sorption capacity and the Benndale (4 % clay) soil had the smallest P sorption capacity. Sorption of P within a soil was affected by the rate of added P and past fertility treatment. Treatment differences in P sorption were due primarily to the level of extractable P and soil pH. Within a given soil, P sorption (at a given rate of added P) generally decreased as the level of extractable P increased. Regression analysis of P sorption data for equilibrium P concentrations of 1 to 32 μmol/L showed that the parti‐ tioning between sorbed and solution P (buffer power) had not been changed by 56 years of annual applications of P. The maximum P sorption capacity of the four soils was decreased slightly by P fertilization.     

Yield of iron‐sprayed and non‐sprayed strawberry cultivars grown on high ph calcareous soil

Abstract

Iron (Fe) deficiency chlorosis (FeDC) results in extensive reduction in yield of strawberry (Fragaria x ananassa Duch.) grown on high pH calcareous soils. Three cultivars differing in response to FeDC were grown on a high pH (8.2) calcareous soil (25.4% calcium carbonate equivalent in surface 20 cm) in the field (Choueifat, coastal area of Lebanon) to determine the effects of FeDC on fruit yield of cultivars sprayed with FeEDDHA [ferric ethylene‐diiminobis (2‐hydroxyphenyl) acetate]. The unsprayed plots were used as a control. No significant interaction (P<0.05) between cultivars x FeEDDHA spray treatment, and no significant differences (P<0.05) between one and two FeEDDHA spray(s)/week treatment was noted for visual FeDC, fruit number, and fruit yield. Sprayed cultivars once a week produced higher yields than unsprayed ones; overall increases were 33% (13% for ‘Motto’, 30% for ‘Chandler’, and 56% for ‘Douglas'). Even though only slight FeDC was noted on the ‘Motto’ cultivar receiving no Fe EDDHA spray, fruit yields were increased when sprayed with FeEDDHA. However, significant increases in yield for ‘Chandler’ and ‘Douglas’ cultivars with severe FeDC ratings were rioted when sprayed with FeEDDHA.     

Influence of chloride on the uptake and trans‐location of phosphorus in potato

Both chloride (Cl) and sulphate (SO₄) were found to impair the uptake of phosphorus (H2³²PO₄) through the roots of potato in a hydroponically conducted experiment. Radioactive phosphorus (³²P) was used as the marker. The presence of either Cl and SO₄ alone in the nutrient solution made no difference on the impairment. Both ions also inhibited the long‐distance transport of P from roots to shoots. The inhibition by Cl was much greater than that by SO₄, and increased with the concentration of Cl rising from 0 to 15.5 mM in solution.     

Foliar uptake of volatilized ammonia from surface‐applied urea by spring wheat

Abstract

Large volatile losses of NH₃ can occur from surface‐applied urea in semi‐arid areas. Our objective was to determine possible absorption of this volatilized N by the crop canopy under field conditions. At two different times during crop growth, ¹⁵N‐enriched urea was surface‐applied at rates equivalent to 100 kg N ha^‐1 to soil contained in trays placed between two rows of spring wheat. Seven days after application, the soil in the trays was removed from the field and analyzed for ¹⁵N content. Addition of HC1 during soil air drying was necessary to prevent volatile losses of ¹⁵N. Of applied urea‐N, 13% was volatilized over seven days at both application times. Of the urea‐N that was volatilized, 15% was absorbed by wheat at the first application time and 7% was absorbed by wheat at the second application time. Plant absorption of urea N (Y, mg) declined with distance from the source (x, cm) following the equation Y=10.95*10^(‐0.0142x). About 90% of absorbed N was within the first three wheat rows. Our findings suggest that a significant portion of ammonia volatilized from top‐dressed urea might be captured by plant foliage.     

Adsorption‐desorption of zinc in mollisols and their relationship with uptake of fertilizer‐applied zinc by rice

Abstract

Zinc (Zn) adsorption in mollisols conformed to the linear form of Freundlich equation. The log K values were positively correlated with silt, clay, and carbonate contents and soil pH, but negatively correlated with sand content. Sequential desorption of adsorbed Zn in 0.05M Ca(NO₃)₂, 0.1M Mg(NO₃)₂, 0.005M DTPA, and 0.1M HCl revealed that weakly and specifically bound fractions of added Zn, which could easily equilibrate with soil solution, were low and decreased with silt and carbonate contents and soil pH. Weakly bound fraction increased with sand content. Strongly bound and complexed fraction of applied Zn was the maximum and increased with clay, soil organic carbon and carbonate contents and specific surface area, but decreased with sand content. The mineral bound fraction of applied Zn was intermediate and increased with silt, clay and carbonate contents, and soil pH and specific surface area. Zinc uptake due to added Zn fertilizer by rice crop (Y) negatively correlated with log K, but positively related to Zn content in the equilibrium soil extract and Zn desorbed in 0.05M Ca(NO₃)₂. Both log K and l/n values together explained 59.5% of the total variation in Y, while Zn content in the equilibrium soil extract, Zn desorbed in 0.05M Ca(NO₃)₂, 0.005M DTPA and 0.1M HCl collectively accounted 79.6% of the total variation in Y.     

Effect of nitrogen on the growth and photo‐synthetic activity of salt‐stressed barley

Pot experiments were conducted in the greenhouse to study the effect of nitrogen (N) nutrition on photosynthesis and water relations of barley plants under salinity conditions. Nitrogen decreased the sodium (Na) content and increased the potassium (K) content in shoots. The net photosynthetic rate of leaves increased significantly with added N increasing from 0 to 100 mg N/kg soil. The activity of ribulose 1,5 bisphosphate carboxylase (RuBPC_ase) in leaves of high‐salt plants was lower, and in leaves of the low‐salt plants higher than that in control plants. The photosynthetic rate was reduced by sodium chloride (NaCl) and was significantly correlated with total soluble protein per unit leaf area. At each N level, stomatal conductance in leaves was reduced considerably by salt. Proline content of leaves increased with increasing N level. It was higher in leaves of salt‐treated plants than in those of control plants. The osmotic potential of leaves decreased with increasing N applied, and the turgor pressure of high N plants remained higher under salt treatment condition.     

Application of capillary electrophoresis on the characterization of cadmium‐induced polypeptides in roots of pea plants

Capillary electrophoresis (CE) has revealed as a powerful technique for a rapid and effective evaluation of the synthesis of polypeptides induced by cadmium (Cd) in root tissues of Cd‐resistant pea plant. CE was performed on root extracts in capillary gel electrophoresis (CGE) using 3% PEG 2November 1998 in Tris‐Tricine buffer as a dynamic sieving polymer solution and in free solution (FSCE) with 0.1M Tris‐Tricine at pH 8.3 as running buffer. By comparison with control, CGE electropherograms of root extracts of Cd‐resistantpea showed a new peak, characteristic of newly synthesized polypeptidic fraction with apparent molecular weight of 10 kDa. In order to get more information, we characterized further the new synthesized polypeptidic fraction as charge to size ratios. Results obtained by FSCE in free solutions showed that polypeptidic fraction split into several components with different charge to size ratios, very close to that of glutathione, the starting molecule for the biosynthesis of phytochelatins. In addition, results suggested a co‐occurrence of MT‐like proteins at low molecular weight and phytochelatins.     

Long‐term supply and uptake by plants of elements from coal fly ash

Abstract

To assess the mineral composition of plants growing in pure fly ash, grasses growing on lysimeters filled with alkaline, neutral, or acid fly ash were sampled several times in a 6‐year period. The samples were analyzed for elements essential for plants and animals as well as non‐essential, but environmentally significant, trace elements. Grasses were also sampled from ash dumps that were 20 and 30 years old. Fly ash is not a proper source of plant macronutrients N, P, and K. Plant growth on the alkaline fly ash can be influenced for some time by the high salinity of that ash. Grasses growing on unweathered fly ash were found to be high in Al, B, Co, Fe, Mo, Ni, Pb, and Se. Concentrations of several elements declined in time but levels of B, Fe, Mo, and Ni were still elevated in grasses on both fly ash dumps. All concentrations, except Al, were lower than toxicity levels for plants as found in literature. In plants growing on fresh fly ash concentrations of Mo, Pb, and Se can exceed the maximum tolerable levels for domestic animals. On weathered fly ashes (ash dumps) the Mo, Pb, and Se concentrations in grasses were below the maximum tolerable levels. Effects on animals by Mo in weathered ash may not be excluded because Mo concentrations can be high enough to induce Cu deficiency. Animals that feed on plants grown on fly ash could suffer from Ca, Mg, Na, and P deficiency.     

Modeling approach to nitrogen uptake by field‐grown corn

Although the plant root system is one of the most important plant parameters affecting nutrient uptake by plants, root studies in field experiments are rarely conducted in plant nutrition and fertility studies. Since collection of root samples and measurements are difficult and time consuming, they are not considered as a routine plant parameter. Therefore, the effect and importance of the corn root system on plant nitrogen (N) uptake and grain yield was studied under field conditions in Adana, Turkey. Nitrogen was applied at rates of 200, 250, 300, and 350 kg N ha^‐1 as urea in a randomized complete block design experiment with three replications. During course of the experiment, soil, plant, root, and grain samples were collected and prepared for chemical analysis. Nitrogen uptake by plants was predicted using a COMP8 mathematical computer model and compared to actual plant uptake. Grain yield and leaf N content increased with increasing N rates, but root length did not change statistically. Predicted N uptake increased with added N, but was much smaller than observed N uptake under field conditions. Consequently, additional soil and plant parameters should be considered in nutrient uptake models to make the prediction more sensitive.     

Effect of PCMBS on calcium‐ or aluminum‐induced curvature in roots of two watermelon cultivars

Unilateral application of calcium (Ca) or aluminum (Al) in agar to the primary roots of watermelon [Citrullus lanatus (Thunb.) Matsum. and Nakai] cultivars ‘Dixielee’ and ‘Mirage’ induced root curvature. Root curvature induced by Al was greater than that induced by Ca in both cultivars. PCMBS inhibited Al‐induced root curvature in both cultivars, but had no effect on Ca‐induced curvature. The inhibition of curvature indicated that PCMBS reduced Al uptake. ‘Dixielee’ was more responsive to PCMBS than was ‘Mirage’.     

Effects of mes [2(n‐morpholino)‐ethanesulfonic acid] and ph on mineral nutrient uptake by mycor‐rhizal and nonmycorrhizal maize

Mycorrhizal (+VAM) and nonmycorrhizal (‐VAM) maize (Zea mays L.) plants were grown in sand culture in a greenhouse to determine effects of MES [2(N‐morpholino)‐ethanesulfonic acid] (2.0 mM) and pH (4.0, 5.0, 6.0, and 7.0) on mineral nutrient uptake. Plants were inoculated with the vesicular‐arbuscular mycorrhizal (VAM) isolate Glomus intraradices UT143. Shoot and root dry matter yields were lower in plants grown with MES (+MES) than without MES (‐MES), and decreased as pH increased. Shoot concentrations of N, Ca, Mg, Mn, and Zn were generally higher in +MES than in ‐MES plants, and nutrient contents of most nutrients were generally higher in + MES than in ‐MES plants. Concentrations of N, Ca, Mg, and Mn increased and P, S, and Fe decreased, while contents of all measured nutrients except Mn and Zn decreased as pH increased. Concentrations of Mn, Fe, Zn, and Cu were higher in +VAM than in ‐VAM plants, and contents of P and Ca were higher in ‐VAM than in +VAM plants and Zn content was higher in +VAM than in ‐VAM plants. MES had marked effects on mineral nutrient uptake which should be considered when MES is used to control pH of nutrient solutions for growth of maize.